1. Field of the Invention
The subject invention relates to a needle assembly for collecting samples of fluid from a patient. The needle assembly includes a needle holder and a needle cannula that can be retracted into the holder after use.
2. Description of the Related Art
A needle assembly is used to acquire a sample of blood from a patient and to deposit the blood sample in an evacuated tube. The tube then is shipped from the site of collection to a laboratory for analysis.
The typical prior art needle assembly includes a needle holder that has opposed proximal and distal ends and a tubular side wall extending between the ends. The proximal end of the needle holder is widely open. However, a wall extends partially across the distal end of the tubular side wall. A needle cannula is mounted to the distal end wall of the prior art needle holder. The needle cannula includes a pointed distal end that extends distally beyond the needle holder and a pointed proximal end that extends centrally within the tubular side wall of the holder.
The prior art blood collection needle assembly is employed by a phlebotomist who aligns the pointed distal end of the needle cannula with a targeted blood vessel. The phlebotomist then gently eases the pointed distal end of the needle cannula into the blood vessel in a procedure referred to as venipuncture. Most phlebotomists prefer to align the blood collection needle assembly such that the beveled distal end of the needle cannula faces up. Thus, the phlebotomist can visually identify the tip of the needle cannula and can properly align the tip with targeted blood vessel. Additionally, most phlebotomists prefer to have the needle cannula aligned at a very small acute angle to the skin surface of the patient. The small acute angle facilitates visual alignment of the needle cannula with the targeted blood vessel and further helps the phlebotomist to gauge the depth of insertion of the needle cannula.
The phlebotomist urges an evacuated tube into the open proximal end of the needle holder after the targeted blood vessel has been accessed by the needle cannula. The evacuated tube is moved sufficiently into the needle holder for the pointed proximal end of the needle cannula to pierce the rubber seal that extends across the mouth of the evacuated tube. Thus, blood from the targeted blood vessel will flow through the needle cannula and into the evacuated tube. This flow of blood into the evacuated tube often is the first indication that the targeted blood vessel has been accessed. Unfortunately this initial observable flow of blood may not appear until several seconds after the venipuncture attempt. On some occasions, the phlebotomist may incorrectly interpret this elapsed time as an indication that the targeted blood vessel has been missed. Thus, a phlebotomist may withdraw the needle cannula and conduct the venipuncture procedure again, thereby causing additional discomfort and trauma for the patient.
Some prior art blood collection needle assemblies are constructed with a transparent flashback chamber for receiving the blood prior to flow of the blood into the evacuated tube. Thus, the flashback chamber can provide an earlier visual indication of successful venipuncture. However, the flashback chamber substantially complicates the prior art blood collection needle assembly and typically will increase both the cost and the size of the prior art blood collection needle assembly.
The tubular needle holder for the prior art blood collection needle assembly typically is about 2 cm in diameter. Additionally, both the proximal and distal portions of the needle cannula are aligned along the axis of the prior art tubular needle holder. Thus, the needle cannula is spaced radially from the tubular side wall of the needle holder by approximately 1 cm. This relatively large radial dimension prevents the phlebotomist from aligning the needle cannula at a very small acute angle during venipuncture. Thus, the standard blood collection needle assembly must be aligned at an acute angle that is larger than the angle preferred by most phlebotomists.
An accidental stick with a used needle cannula can be very painful and can transmit disease. Consequently, most prior art blood collection needle assemblies are constructed to reduce the risk of accidental needle sticks. For example, some prior art blood collection needle assemblies have actuators that enable the used needle cannula to be released from the needle holder and into a sharps receptacle without manually unthreading the needle cannula from the needle holder. Other prior art blood collection needle assemblies have a shield that can be moved distally along the needle cannula or that can be rotated into surrounding relationship with the needle cannula. Many prior art shields add to the cross-sectional dimensions of the needle holder, and hence further increase the minimum possible acute angle alignment of the needle cannula for venipuncture. Some prior art shields for blood collection needle assemblies visually obscure the distal end of the needle cannula and/or the evacuated tube. Hence, these prior art shields can impede the view of the collected blood that is required to assure a successful venipuncture. Other prior art shields are sufficiently cumbersome that the phlebotomist may defer employing the shield, thereby creating a significant risk for an accidental needle stick.
In view of the above, an object of the invention is to provide a blood collection needle assembly that has the distally directed needle cannula positioned and aligned to facilitate venipuncture.
Another object of the invention is to provide a blood collection needle assembly with a blood flashback indication to provide accurate and early evidence of an acceptable venipuncture.
A further object of the invention is to provide a blood collection needle assembly that enables an efficient and safe shielding of the needle cannula.